Sealed-in conductor



March 24. 1925.

P. K. DEvERs SEALED-IN CONDUCTOR 4 Inventor; A. i .Oe Vers.

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lllllll A50 production of seals may be carri Passed Mar. 24, 1925.

UNITED STATES 1,531,265. PATENT OFFICE.

PHILIP K. DEV'ERS, 0F LYNN, IASSACHUSETTS, ASSIGNOR TO GENERAL ELECTBI COMPANY, A. CORPORATION F NEW YORK.

SEALED-IN CONDUCTOR.

Application led August 3, 1921. Serial No. 489,630.

To all whom it may concern:

Be it known that I, PHILIP K. Dnvnns, a citizen of the United States, residing at Lynn,- in the county of Essex, State of Massachusetts, have invented certain new Aand useful Improvements in Sealed-In Conductors, of which the following is a specification.

The present invention .comprises a new l) electric current-conducting seal and the method of making the same. Altho a seal embodying my invention maybe used for a variety of purposes it is the especial object of my invention to provide a seal suitable for use 13. with vessels of fused silica or quartz glass as it is commonly known.

The substantially zero coeiiicient of thermal expansion of silica. precludesvthe seal. ing-in of the conductors by methods comf) monly used for electric apparatus consisting of glass. Moreover, Athe high melting point of silica requires that a commercially usable seal for fused silica have a relatively simple geometric form. As far as I am aware, commercially useful seals in vessels of fused silica prior to my. invention have been made by interposing glasses of varying composition between the fused silica and the wire or other conducting body ofthe seal. l

Iy have discovered that it is possible to maintain quartz glass, especially when in the form of a thin-Walled tube, under compression by a body of metal having a suitable coeilicient of expansion so that a tight 33 joint will be maintained between the quartz glass and a sealed-in conductor. As will be pointed out with particularity in the appended claims, a seal embodying my invention is made by applying an envelope of 4U molten metal about a tube of quartz glass while a conductor is present within the tube, and allowing this envelope to cool and contract or expandupon the wall of silica thereby gripping the same.

Figs. 1, 2, 3, and 4 show in longitudinal section various stages in the production of my improved seal, and Figs. 5, 6 and 7 are longitudinal sections of modifications.

Referring to Fig. 1 the first ste in the out by reducing an extension 8 in the container 9 in the form of a relatively thin-walled tube, and inserting 'a wire or other conductor 10,

which may be connected to electrode 11, for

example, and which may consist of tungsten,

iron, nickel, or other'suitable material. The tube 8 preferably has a greater length than its wall diameter, and the container 9 may be evacuated or not, as desired. The conductor 1.0 maybe connected to an elec- 00 trode 11. f-

The parts thus assembled next are dipped into a body `of ,molten4 metal 12 contained within a. crucible 13. The bod of metal 12 may-consist of iron, a suita. le ferrous G5 alloy, nickel or other suitable metal having a materially greater thermal coeicient of expansion than silica. The metal 12 is permitted to cool and' solidify about the quartz wall 8 thereby shrinking and gripping the silica. The container 13 then may be removed and "the end of thesilica tube with the surrounding` metal may be cut awa as indicated in Fig. 3, exposing the enfl7 of the wire 10. During this operation gas will not leak between the silica wall and the wire 10, but to completely protect the seal it is desirable to provide a cap 14 of metalas indicated in Fig. 4. The cap 14 may be constituted of the same metal as the shell 12 but almost any metal can be used. ""It may be applied by fusing the end of a .wire and directing the drops of fused met-al. against the end of the seal. Preferably the shell. 12 is thinner walled near .the junction 85. of the extension 8 with the container 9 than at sthe more remote portion, as indicated in the drawing. In some'cases it 1s desirable to provide an enlargement or bead 15 in the tube 8 adjacent to its junction with the main bodyv of the container 9 inl order to minimize danger of cracking the tube 8 at this region and to provide /addltional means for the metal to grip the quartz.

It is not necessary that the conductor 10 90 make a. tight fit within the tube 8. As shown in Fig. 5, the conducto-r1() may it loosely within the tube so that molten metal will be drawn into the space between the conductor and the surrounding tube 8, the4 end of which is open as indicated. In that case a. metal Aof lesser expansion coefficient than quartz. may be used asnpon solidlication as the inner core llj'fvll place the quartz tube 8 under compression.

The space between .thelco'nductcr 10 and the inner wall of the'tube 8 is'shoWn somewhat exaggerated in order jto render the drawing clear.

In some cases the cond-unter 10 withinthe 110 tube may be entirely omitted. As shown in Fig. 7 a portion of the body of molten metal being drawn by vacuum or anysuitable Way into the tube 8. Contact from internal conducting' bodies such as electrodes or the like to the filling of metal within the tube 8 may be made in any desired Way.

This modification of my seal will be particularly advantageous when contact is to be made to a body of mercury or other conducting material.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A current conducting seal comprising the combination of a tubular member consisting of fused silica, a body of metal having a different coellicient of thermal expansion than silica shrunk about said tubular member so that said member is'maintained under compression. d i

2. A current conducting seal V'comprising the combination of a thin-Walled tubular member consisting of fused silica, a wire passing'thru the bore of said tube and a body of metal cast about said silica tube and making contact with said wire.

3. A 4current-conducting seal comprising the combination of a container, a tubular member consisting of fused silica, having greater length than diameter joined to said container at oneI/end, a conductor passing thru the bore of said tube, a shell of metal having greater coeiiicient of expansion than silica shrunk upon said tube and a metal cap upon the free end of said tube joined both to the conductor Within the tube and the shell surrounding the tube. l

4. A seal comprising the combination of a tube consisting of fused silica, and a body of metal having a greater coefcient of expansion than silica cast upon the exterior of said tube over a length materially greater than the diameter of said tube and enclosing the mouth of said tube.

5. 'Ihe method of making a current conducting seal for a container of quartz glass which consists in producing a tubular extension upon said container having a length in excess of the diameterl thereof, inserting a conductor into said tube, surrounding said tube by a .layer of molten metal having greater coeiiicient of expansion than quartz, and permitting said metal to solidify.

6. The method of making a current conducting seal in a quartz container which consists in forming a tubular extension in the Wall of said container,finserting a conductor lnto the bore of said'tubular extension, surrounding said tubular extension by an envelope of molten metal having an appreciable thermal coefficient of exf ansion 7. A composite body of silica and a4 metal metal surrounding and gripping the silica, l

said metal being shrunk upon fthe silica by solidifying in place from a fused state.

8. A gas-tight composite body of silica and a metal comprising a mass of silica, a core of metal therein having a higher temperature coeiicient of expansion than silica, and a mass of metal surrounding saidv silica mass, said metal also having a higher coeiiicient of expansion than silica.

9.l A container consisting of silica glass having a tubular extension, an electrode within said container, a conductor connected to said electrode and passing through the bore of said extension, a body of metal surrounding said extension and entering into the bore thereof.

10. The combination of a container of silica glass having a tubular extension, a body of metal enclosing the extremity of said extension and entering the bore thereof,

said metal being solidified in placefrom a fused state.

11. The combination of a container of silica glass having a thin-Walled tubular extension, conductors respectively lling and surrounding said extension, and placing the 4Wall of said tubular extension under compression.

12. A container consisting of silica glass and having a tubular extension, a conductor filling the bore of said extension, and a body of metal surrounding said extension .and being shrunk thereon by cooling from a fused state, the thickness of said exterior metal body being less near the junction of said extension and the container.

13. The process of providing a sealed-in conductor in a vessel of silica glass which consists in producing a tubular extension of the wall of said vessel at the region said conductor is desired, surrounding said extension and filling the bore thereof with molten metal, and allowing said metal to cool and shrink upon said extension. 0

14. The process of sealing a leading-1n conductor into containers of quartz glass which consists in imbedding said conductorv in a tubular extension of 'said container and shrinking upon saidextension a metal from. the fused'state. v

15. .The method of sealing a conductor into a quartz tube which consists in causing molten metal to solidify in contact with both the inner and the outer surfaces of said tube, said metal being chosen to have a coeicient 1 of expansion su'iciently high to cause the' resulting offre and shell to hold said silica tube under compression.

In Witness whereof I have hereunto set my handthis 1st day of August, 1921.

PHILIP K. DEVERS'. 

